Docs: Add modular architecture notes

README.md

@@ -1,2 +1,18 @@
 # vibegif.lol
 AI Generated Gifs (BYOK OpenRouter)
+
+## Modular structure
+
+- `index.html` → UI markup only
+- `src/main.js` → app orchestration
+- `src/app/dom.js` → DOM/UI helpers
+- `src/core/storage.js` → API key persistence
+- `src/core/messages.js` → prompt builders
+- `src/services/openrouter.js` → OpenRouter API client
+- `src/services/gif.js` → GIF assembly logic
+- `src/styles.css` → shared styles
+
+## Why no `vite-plugin-html-inject`?
+
+Not required for this refactor.  
+We reduced complexity by extracting logic into JS modules, keeping dependencies minimal and behavior unchanged.